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Ratios again...

Posted: Sun Dec 02, 2018 12:58 pm
by xvivalve
I've always liked the early Dolomite clock faces and aspire to install them in a Sprint.

Yesterday, I acquired a 2.5 PI speedo which has the correct 140 mph calibration...only to be immediately disappointed to see that it reads 840 revolutions per mile rather than the Dolomite 1000 revolutions per mile.

Now, I could go to the effort of calculating the differences caused by the different axle ratios and wheel circumferences, and then see if I can determine and source a speedo drive toothed to suit to make the clock read accurately....or I could ask if anyone has done so before!? :wink:

Re: Ratios again...

Posted: Sun Dec 02, 2018 2:38 pm
by red&black
I haven't done it but how about recalibration by someone like Speedograph Richfield or Speedy Cables?- If they're still going that is.

James

Re: Ratios again...

Posted: Sun Dec 02, 2018 2:57 pm
by Galileo
Why not just swap the gears inside the speedo with a 1000 TPM one and then calibrate by moving the needle on it's shaft? Think it's 820TPM for the 2.5PI not 840.

Re: Ratios again...

Posted: Mon Dec 03, 2018 9:06 pm
by tony g
If you do decide to remove the speedo needle, first remove the "peg" that stops the needle going further down and note where it lies in its non pegged position. Replace the needle in the same place then replace the peg and all being (calibrated') well it'll perform as expected :)

Tony